1. Field of the Invention
The present invention relates to an image display device which can control brightness in response to a quantity of electric current which is applied to display elements or a light emission time, and more particularly to an image display device having self-luminous light elements represented by organic EL (Electro Luminescence) elements or organic light emitting diodes (OLED) as the display elements.
2. Description of the Related Art
Thanks to the popularization of various information processing devices, various image display devices exist corresponding to roles. Among these image display devices, a self-luminous image display device has been attracting attentions, and an organic EL display has been attracting attentions particularly. Light emitting elements such as OLEDs used in the device are self-luminous and hence, a backlight is unnecessary whereby the organic EL display is suitable for lowering the power consumption. Further, the organic EL display possesses advantages such as the high visibility of pixels or a rapid response speed compared to a conventional liquid crystal display. Further, the light emitting diode has characteristics similar to characteristics of a diode and can control brightness in response to a quantity of electric current which flows in the element. A driving method of such a self-luminous image display devices is disclosed in JP-A-2006-91709 or the like.
As the characteristic of the light emitting element, an inner resistance value of the light emitting element changes depending on a use period or a surrounding environment. Particularly, the light emitting element possesses the characteristic that when the use period is prolonged, the inner resistance of the display element is increased with time so that an electric current which flows in the display element is decreased. Accordingly, for example, when the pixels on the same portion within a screen such as the pixels which form a menu display are turned on, a phenomenon that burn-in appears in the portion arises. In the conventional correction of such a phenomenon, there has been known a method which detects a state of the pixels at the time of starting the image display device, holds the detected state in a memory, and superposes a differential between the display data and the held detection value at the time of operating the image display device to the display data. With the use of such a correction method, however, when the pixels are degraded in spite of a demand for the maximum brightness based on the display data, the pixels cannot perform a display of more brightness. Accordingly, there arises a drawback that the maximum brightness is lowered, that is, contrast is lowered.